How Galileo Galilei made calculations for the Statue of Philip IV in Madrid


Does a sculptor have to resort to mathematics to make a statue? Moreover, would he need a wise man like Galileo Galilei? Well, as incredible as it may seem, that happened in Madrid in the middle of the 17th century: between 1634 and 1640 the Italian artist Pietro Tacca had to ask the famous sage to help him with his calculations when making the equestrian statue commissioned by King Philip IV, the same one that can be seen today in Plaza de Oriente in front of the Royal Palace. What was so important as to require such an extraordinary intervention?

Philip IV wished to see his image sculpted on a horse in a corvette (rampant), as Velázquez himself had painted in the picture currently on display at the Museo del Prado, something unheard of in European sculpture until that moment.

The problem was that, since the animal had its fore legs raised, the front part of the statue would weigh too much and would not support itself; in fact, such a statue was unusual at the time. The key was to firmly anchor the hind legs and the tail to the base but it still seemed insufficient, considering that the figure had to be bronze and therefore hollow.

The sculptor, who made the work in Florence, thought to ask his compatriot Galileo to precisely calculate the tons of bronze needed, as well as the inclination angle for the horse.

I am not going to detail all the numbers here; suffice it to say that the Pisan established in his physical-mathematical study that it would take eight tons of metal and that the back of the saddle would have to be solid in contrast to the forefront, very light, to act as a counterweight.

Photo Alvesgaspar on Wikimedia Commons

Tacca made the wax model following these instructions and then proceeded to the usual technique of casting the mold and pouring the molten bronze. A month later, already cold, the statue was placed on its stand, it was 1642. Not in Plaza de Oriente – which did not yet exist – but in Retiro Park, and it has survived to this day with multiple transfers, being definitively placed in its current location on 17th November 1843, which proves that Galileo’s calculations were correct.

Tacca, on the other hand, has gone unnoticed in history, perhaps because the wax head of the statue had to be replaced – before applying the bronze – by another one by Martínez Montañés, which does not look too much like the monarch. Even so, it is worth a visit to admire it.

Sources: Cervantes.es / Wikipedia.